diff --git a/netlib/http.py b/netlib/http.py
index acd9d85e3..88e66ce46 100644
--- a/netlib/http.py
+++ b/netlib/http.py
@@ -145,8 +145,11 @@ def parse_http_protocol(s):
     if "." not in version:
         return None
     major, minor = version.split('.')
-    major = int(major)
-    minor = int(minor)
+    try:
+        major = int(major)
+        minor = int(minor)
+    except ValueError:
+        return None
     return major, minor
 
 
diff --git a/test/test_http.py b/test/test_http.py
index 206fc4dfa..0174a4aa5 100644
--- a/test/test_http.py
+++ b/test/test_http.py
@@ -106,6 +106,8 @@ def test_read_http_body():
 def test_parse_http_protocol():
     assert http.parse_http_protocol("HTTP/1.1") == (1, 1)
     assert http.parse_http_protocol("HTTP/0.0") == (0, 0)
+    assert not http.parse_http_protocol("HTTP/a.1")
+    assert not http.parse_http_protocol("HTTP/1.a")
     assert not http.parse_http_protocol("foo/0.0")
     assert not http.parse_http_protocol("HTTP/x")